As voice calls or data are routed through a telecommunications network, the information travels through many fiber-optic segments, which are linked together using cross-connects. Typically, information (e.g., packets of data) is converted from light into an electronic signal, routed to the next circuit pathway, and then converted back into light as it travels to the next network destination.
An optical cross-connect (OXC) in the physical layer of an optical network is a fundamental building block used to terminate and administer communication circuits. An OXC allows the installation of new terminal equipment along an optical network. In general, connection points are established at the nodes of an optical network. New terminal equipment is coupled at these connection points. Typically, at the OXC, circuits are joined with patch cords, which are cables with connectors on each end. These patch cords could be configured as either simplex (one fiber per cable) or duplex (two fibers per cable).
Fiber optic connectors offer a mechanical means to terminate optical fibers to other fibers and to active devices, thereby connecting transmitters, receivers and cables into working links. Typically, optical fiber cables prepared, run, and thereafter terminated using well-known techniques such as splicing (typically used with single mode fibers) or connectorizing (commonly used with multi-mode fibers).
Splicing is a method of joining two bare fibers permanently together using a mechanical or a fusion splice. This method is generally used either to connect two cable runs together to make a run longer, or to add a pigtail connector--a short piece of cable with a factory-attached connector at one end--onto the cable. Splicing is typically done by carefully aligning the cores of the two fibers, and either fusing (melting) them with an electric arc, or by using a mechanical method wherein the fibers are glued or gripped together by means of a ferrule, which is a fiber optic connection component that holds a fiber in place and aids in its alignment.
Persons of ordinary skill in the art are aware of several methods of connectorizing. These methods include the following.
(a) Thermal Cure Epoxy method, which uses either heat-cure epoxy or five minute (ambient) epoxy to cure fiber into ferrule, and after curing, the fiber is scribed and polished to a fine flat end surface. PA1 (b) Cleave and Crimp method, which uses a pre-loaded fiber stub into ferrule, allowing a user to prepare fiber and jacket and then cleave the fiber to a pre-established length, after which the fiber is inserted into a plug and crimped into place. PA1 (c) Ultra Violet (UV) Adhesive method, which uses a technique similar to the thermal cure epoxy technique, with the exception that the fiber is bonded via a UV adhesive and the use of a UV source such as a UV lamp or sunlight to cure the epoxy. PA1 (d) Epoxyless method, which uses a body technique where the fiber and cable are crimped to a plug body before mounting the plug into a tool that forces a plunger forward, forcing a resilient sphere to provide a compression-fit over the fiber.
A paper by Sjolinder entitled "Mechanical Optical Fibre Cross Connect" discloses a remotely operated fiber crossconnect (FXC) based on mechanical movements of fiber connecters. This FXC comprises linearly moving electric motors on two sides of a matrix base plate. The motors on one side of the matrix base plate move in a direction perpendicular to those on the other side and move the fiber to a certain position in the matrix. The motors assemble connectorized fibers together in what are called "locomotives," each of which locomotive contains two motors. This type of assembling forms a connection, which process is called "mating." After mating two ferrules together, which are previously assembled in a v-groove to form a "block", a force is applied to press the two ferrules closely together. This design has an advantage in that a connection that does not require a reconfiguration can stay in place while others are being reconfigured.
Sjolinder, however, requires 4N motors, where N is the number of input fibers, one for each ferrule. One of these motors is used to move the ferrule into position and one to perform the mating action. Thus, for a crossconnect with 256 inputs, Sjolinder requires 1024 motors. It would be advantageous to design a robotic optical crossconnect that requires fewer motors irrespective of the size of the crossconnect.